Developing new starters for fermented milk products

The production of fermented milk products has evolved from a cottage industry to a large scale, factory-based manufacturing process within a century. One consequence of this rapid evolution of technology has been that the demand for suitable starter strains has become more stringent. A satisfactory dairy fermentation requires a stable, predictable rate of acid production. Phage infection must not be allowed to interfere with this. Ultimately the fermented product must develop a desirable, long-lasting flavour - preferably after spending the minimum time in storage. The development of successful starter strategies to meet these requirements has involved the application of established bacteriological techniques with particular care being devoted to strain characterisation. Detailed analyses of the molecular genetics of different lactic acid bacteria has been feasible for little more than a decade, but the tempo of discovery has increased dramatically throughout this period. For Lactococcus lactis, which is a commonly used starter for cheese manufacture, the situation now exists where there are excellent prospects for directed molecular approaches to strain improvement. Thus, with the aid of biotechnology itshould be possible to identify and/or construct starter strains that have : good flavour-producing characteristics, satisfactory rates of acid production and improved phage resistance properties.